According to 46 CFR §56.07-10, the rated relieving capacity of safety and relief valves used solely for the protection of piping systems must be certified by the manufacturer at what percentage of the valve's set pressure?

Why C is correct

46 CFR §56.07-10(b)(2) states that the rated relieving capacity of safety and relief valves used in the protection of piping systems only must be based on actual flow test data and the capacity must be certified by the manufacturer at 120 percent of the set pressure of the valve.